Too Long; Didn't Read
Developer and designer of Cantabile — software for performing musicians. "DocBrowser" is a nice HTML template for documentation. The DocBrowser documentation itself uses the template. The navigation tree is the most prominent part of DocBrowser is the navigation tree. "On this page" links are created automatically from article headings that have an id attribute. You can also customize the text displayed in the side bar with a data attribute on the heading. The template is available as a.zip file (get it here) that includes the styles sheets, script files, the custom font and a heavily commented layout file.